The present invention relates to a spectroscopy cell. It particularly relates to a method and means suitable for providing a low volume flow-through cell for spectroscopy, especially for samples at extreme temperatures.
There is a requirement to provide a spectroscopy cell to examine such processes as gas-solid interactions, often required in the field of catalyst research and other research areas. In some such studies the flow of a gas across a solid material must be controlled so that the gas volume is low and so that the flow path is exposed to the optical beam of the spectrometer, often arranged so that the beam interacts with the region of the solid first contacted by the gas. Such arrangements are necessary to enable meaningful time based studies of the gas-solid interaction as a function of temperature and other experimental parameters. A preferred embodiment of this invention provides a method by which the maximum temperature can be substantially increased over methods previously developed and providing much lower volumes than available from methods previously developed while meeting the requirements for a well defined gas flow path. The invention is not restricted to a particular optical range or to a particular optical technique or to a particular sample format or to a specific sample material or gas or fluid.
Rossiter (U.S. Pat. No. 4,674,876) has shown how very high sample temperatures can be achieved in a gas environment with spectroscopic access. But that invention does not address the problem of providing a very low gas volume (less than 10 ml) around the sample region. There are a number of difficulties in defining a low gas volume in the region of a sample to which there is to be optical access and around which a well defined gas flow path must be maintained. The difficulties are compounded by differential thermal expansion and the requirement to maintain gas connections as the temperature of the sample is varied. At the temperatures addressed here (in excess of 300 deg C. or below 0 deg C.), where conventional sealing methods (such as polymeric o-rings) cannot be used in contact with the sample region, yet it is necessary to provide gas connections and define a flow path in this region of high or low temperature.